Many of my kits are not purchased with the 'Hot' option shown in the first post. So it is possible that the person you bought it from, had a linear driver in there. Or some other driver rather than the FlexDrive shown here in this thread.

If it's a Jib driver, then you want 2 X Li-Ion's. If it's a FlexDrive, then you want a single 18650...

Although now I'm more confused... driver already handled 8.4v, two freshly charged 18350 batteries each at 4.2v just fine, with about 10 minutes of total run time off of those batteries.

I thought it was a linear driver... so originally used the 18350 batteries. Only found it to work almost equally as well with a 18650 battery, when playing around with the lpm last night out of curiosity.

I have another c6 build which is a linear jib and while it does ~1.2W with two 3.7v batteries, it puts out a <100mW with one 18650 battery.

At least got an interesting experience out of it. As I was twisting on the tailcap the laser lased... even though the tailcap was in the off position. Once I twisted it on, and clicked it, that was it.

Obviously didn't lpm it, but it did leave a mark on my white wall, 3 feet away. Last laser to do that was an 800mW 405nm.

I opened it up, slight smell of burned electronics. Hopefully the diode is fine and I just killed the driver.

I guess before the driver was able to handle the increased voltage.. but not with the batteries freshly charged.